Photo: "Makeover" Birds Get Testosterone Jolt

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A researcher holds three naturally colored barn swallows from New Jersey in an undated photo.

Male birds who got richly colored "makeovers" from scientists attracted more females and made competing males jealous—giving them a powerful surge in testosterone levels, a new study reveals.

The research suggests that social feedback on a daily basis can affect an animal's physiology.

Photograph courtesy University of Colorado, Boulder

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